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The evidence supports an increased risk of HIV acquisition when the uninfected partner has an STD. It is unclear, however, what the most appropriate estimates are for each population, behavior, and type of STD given the observational nature of these kinds of studies. Several studies have found that ulcerative STDs may confer higher risk (e.g., risk ratio ranges from 2.2 to 11.3) than non-ulcerative, inflammatory STDs (e.g. risk ratio ranges from 3 to 4) (Fleming, 1999; Galvin, 2004; Berman, 2006). However, an updated systematic review of the published literature is needed for more accurate risk estimates by population, behavior, and type of STD.

Although no direct empirical evidence has been identified for MSM at this time, it is biologically and epidemiologically plausible for STDs to also increase the risk of HIV acquisition among HIV-negative MSM. The estimate for heterosexual men and women is the best proxy estimate for MSM until more direct evidence is available.

Ulcerative STD Infection of HIV-Positive Persons

Having an STD more than doubles the risk of an HIV-positive heterosexual man or women to transmit HIV during sex to his/her uninfected heterosexual partner.

MSM

2.58

Gray 2001

There are no empirical data providing a direct estimate for MSM. Biological and epidemiological theories provide indirect evidence that ulcerative STD infection has similar effects on HIV risk among MSM.

Having an STD more than doubles the risk of an HIV-positive heterosexual man or women transmitting HIV during sex to his/her uninfected heterosexual partner.

Strengths and Limitations of Risk Estimates:

Gray, 2001 is a longitudinal cohort study of 174 monogamous discordant heterosexual couples, with 38 HIV transmissions to uninfected partners, from a larger Rakai (Uganda) community-randomized trial of STD control for AIDS prevention. This risk estimate for ulcerative STDs is specific to the presence of genital ulceration.

The evidence suggests an increased risk of HIV transmission due to the HIV-positive partner having an STD. It is unclear, however, what the most appropriate estimates are for each population, behavior, and type of STD given the observational nature of these kinds of studies. Indirect evidence of STDs increasing the infectiousness of HIV exist. Ulcerative STDs generally increase HIV shedding in the genital tract and inflammatory STDs increase the concentration of HIV in the urethra, semen, and cervical fluid (Galvin, 2004). An updated systematic review of the published literature is needed for more accurate risk estimates by population, behavior, and type of STD.

Although no direct empirical evidence has been identified for MSM at this time, it is biologically and epidemiologically plausible for STDs to also increase the risk of HIV transmission among HIV-positive MSM. The estimate for heterosexual men and women is the best proxy estimate for MSM until more direct evidence is available.

Acute HIV Infection

The risk of HIV transmission during acute infection is about 7.25 times the risk during the middle stage of HIV disease among heterosexual men and women.

MSM

7.25

Wawer, 2015

There are no empirical data providing a direct estimate for MSM. It is biologically plausible for acute infection to have a similar effect on HIV transmission among MSM.

The risk of HIV transmission during acute infection is about 7.25 times the risk during the middle stage of HIV disease among MSM.

Strengths and Limitations of Risk Estimates:

Wawer, 2015 estimates the increased risk of HIV transmission due to acute HIV infection from a retrospective sub-sample of 235 monogamous, HIV-discordant heterosexual couples with follow up time from a larger Rakai (Uganda) community-randomized trial of STD control for AIDS prevention. This study looked at early-stage infection (defined as up to 5 months after seroconversion, a 2.5-month midpoint), established infection or “middle” stage of infection (>6 months after seroconversion), and late-stage infection (6 to 25 months before death).

No other published study of empirical data on increased risk of HIV transmission during acute infection exists.

Acute HIV infection is clinically defined as the time between viral infection and development of detectable antibodies against HIV-1. During this time, concentrations of HIV in blood and semen are highest and transmission risk is therefore greatest; this period typically last a few weeks (Cohen, 2005; Pilcher, 2004). Pilcher, 2007 estimated that viral load reaches its peak at 17 days after seroconversion in blood and around 4 weeks after seroconversion in semen. A modeling paper (Pilcher, 2004) estimated the probability of heterosexual transmission of HIV during acute infection is ~8 to10 times the probability during later stage of infection, where the viral load peak in semen was modeled at about day 20 after infection.

Although no direct empirical evidence has been identified for MSM at this time, acute infection is likely to also be associated with increased HIV transmission risk among MSM. The estimate for heterosexual men and women is the best proxy estimate for MSM until more direct evidence is available.